{"id":2755,"date":"2021-01-05T15:48:55","date_gmt":"2021-01-05T15:48:55","guid":{"rendered":"http:\/\/julius-ihle.de\/?p=2755"},"modified":"2021-05-02T14:25:02","modified_gmt":"2021-05-02T14:25:02","slug":"playing-with-osl-4-udim-mask","status":"publish","type":"post","link":"https:\/\/julius-ihle.de\/?p=2755","title":{"rendered":"Playing with OSL #4: UDIM Mask"},"content":{"rendered":"

\"b_udimmask\"<\/a>
\nIt’s been a while… Busy days :)<\/p>\n

Occasionally there might be the need for LookDev Artists to adjust areas of a shader based on different UDIMs. If an asset has a continuous mesh that is only separated by UDIMs (eg nails on a character or decorative parts of clothing) it can be useful to create masks for specific UDIMs in the shading network to isolate areas of interest.
\n<\/p>\n

It is relatively straight forward to get the integer values of each UDIM in a shader by just creating a Nodegraph that resembles the UDIM formula:
\n1000+(floor(u)+1)+(floor(v)*10)<\/em><\/strong><\/code><\/p>\n

You can output the result into a compare node in your renderer of choice and check whether it matches against a certain UDIM. While this is fine for 1 or 2 UDIMs it gets quite cumbersome with many UDIMs.<\/p>\n

As I like playing with OSL I put together a version that allows you to create masks from a specified list of UDIMs. It expects a comma-separated list of UDIM tiles. You can also specify ranges. Eg 1001,1003-1006,1015,125<\/em><\/strong> will select the following UDIMs: 1001,1003,1004,1005,1006,1015,1025.
\nYou can also just output the raw UDIM tiles integers if you want to create more complex masks downstream.<\/p>\n

There are just a few caveats:
\n1) The input is a string, so internally it’s checking against a regex to see if the passed input is a valid list of UDIMs. This can potentially be expensive in larger shading networks.
\n2) At the moment there’s a hard-coded maximum of 10 entries that are allowed for performance reasons (note that ranges such as 1001-1005 count as 1 entry). You can edit the #define MAX_TILES 10<\/code> in the supplied .osl file if you need more.
\n3) At the moment I could only test it with Arnold. Not sure if Blender supports UDIMs properly in this way. RenderMan should work as well.<\/p>\n

You can download it HERE<\/a> from github.<\/p>\n

Here’s a quick demo:
\n